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E46 (1999 - 2006) The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

My 2001 325i idles rough at stops and in park. It has progressively gotten worse and even died once today. It doesn't do it all the time, just randomly. I'm new to the site and don't know much about what's what under the hood besides the basics. Any ideas?

Well, you have a LOT of reading to do. Take a look at the WIKI at the top of every page, and then SEARCH 'till your eyes bleed. There really is a LOT of information on rough idle conditions. Good luck.

After your reading adventure, come back and let us know what you found.

Could be a lot of things. When it happened to my ZHP it just ended up being a dirty MAF. It could also be a camshaft position sensor, a vacuum leak, VANOS, and probably a few other things that aren't coming to my mind right now

My car did the same and it was a misfire. Go to autozone and they will plug into the computer and give u all the codes for free and it will tell u if you have a cylinder misfiring. Which if it is its probably a coil or a spark plug both easy fixes Do It Yourself and save money.

Go to autozone and they will plug into the computer and give u all the codes for free.

Just for the record ... that won't work in all states as some make it illegal for Autozone to do the free check...
- Where it's illegal for auto parts stores to lend you an OBDII scanner for free (1) (2)

But, luckily, a decent scanner is only $22 ...
- Where to get the cheapest reasonable ODII scanner in the world (1) (2)

I had this same problem. I had a huge tear in the air intake hose (upper boot). The rubber gets old and dry over time and can develop cracks. A crack in the hose causes rough idling to the point of stalling. Replace the upper and lower boot (the lower one is very hard to remove because of the position of the hose clamp screw).

While your at it. take out your ICV ( Idle Controller Valve) and clean it with carb and throttle cleaner, easy if you can take off the lower boot first.

Also Clean your MAF which is connected to the upper boot air intake hose. Once you do this your car should idle much better.

Once your car is idling better but not perfect you can replace the idle pulley and perhaps replace the belt while your in there. All these things are cheap to do.

I found a thread from 2010 on this forum; a person had rough idling and cleaned his intake vanos solenoid which he said is simple to do. Afterward he had a nice smooth idle with no stumbling. posted 3-27 2010 by brentboshart - "Rough Idle when cold solved"

My idling after I replaced the air intake hose was much better but not as smooth as it was before I began all my maintenance work. I replaced the oil filter housing gasket which ment taking of the fan, belt, idler pulley, alternator and finally the housing plate. Then putting it all back when the gasket was replaced -*Whew*. When I did all that I had the idling problem and the SES light came on. Ah well.

Through it all I have learned alot about the car and am fairly confidence I'll get my car back in excellent condition. It is after all an eight year old car and parts need to be cleaned and replaced. I live in an area that heavy with pollen in the air, when I open the hood for the first time in many months I was astounded at how dirty it was. Pollen was in every nook and cranny.

I've got to get a flexible screw driver so that I can replace that lower air intake hose (the screw is so hard to get to) - I want to clean the Idler control valve (ICV) was had taken off the DISA box and wonder if I should clean the paddle connected to it. It was coated with oil. But I put it back the way it was. I only wanted to deal with one issue at a time.